Video image distribution apparatus, control method, and recording medium

ABSTRACT

A video image distribution apparatus includes a reception unit configured to receive a video data distribution start request from a client apparatus, an extraction unit configured to extract, from the video data distribution start request, information indicating a client time measured by the client apparatus as a transmission timing at which the client apparatus transmits the video data distribution start request, in a case where the extraction unit receives the video data distribution start request, a first determination unit configured to determine a video data distributable time based at least on the client time, and a transmission unit configured to transmit the video data distributable time to the client apparatus.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a video image distribution apparatus, acontrol method, and a recording medium.

Description of the Related Art

The number of distribution systems using an Internet Protocol (IP)network such as the Internet has been increasing. Such distributionsystems are used in, for example, Internet sites for distributing theconditions of ski areas, zoos, etc., and for monitoring shops,buildings, etc. In the field of moving image services, streamingtechniques such as Dynamic Adaptive Streaming over Hypertext TransferProtocol (HTTP) (DASH) and HTTP Live Streaming (HLS) implemented mainlyby Apple Inc. are increasingly used. They are techniques that arestandardized by the Moving Picture Experts Group (MPEG). In the videoimage distribution techniques, issues of the Real-time TransportProtocol (RTP) are solved, such as a network environment issue and anissue that a special client application is required. Specifically, thevideo image distribution techniques enable reception and reproduction ofmoving image distribution on a normal browser.

In general DASH distribution, a distribution server divides a pluralityof moving image data of different resolutions and bit rates into movingimage files referred to as segments of a unit of several seconds. Then,a client sequentially downloads and reproduces the moving image filesthat are most suitable for its display capacity and communication bands.Specifically, the client first acquires a media presentation description(MPD) file in which entire moving image information is described, andthen selects a moving image stream of a suitable resolution or bit ratefrom the MPD file. Then, the client downloads and reproduces movingimage data of a MPEG-2 transport stream (TS) or MPEG-4 (MP4) file,segment by segment, based on the description of MPD.

In the MPD file, a distributable time (availability start time, etc.) isdescribed. Thus, especially in live distribution, the client can deferacquisition of moving image data until the distributable time, or theclient can acquire moving image data from current moving image data ifthe distributable time has been passed. Thus, it is important tosynchronize the time in advance between the distribution server and theclient. Meanwhile, Japanese Unexamined Patent Application Publication(Translation of PCT Application) NO. 2016-509400 discusses a techniquethat the time at which content data is retrievable and a timesynchronization method are included in a MPD file and a clientsynchronizes the time using the time synchronization method described inthe MPD file.

The conventional technique, however, requires the time of a clientapparatus to be changed in order to view moving image data. An improvedsolution is therefore desired.

SUMMARY OF THE INVENTION

The present invention is directed to a mechanism by which a clientapparatus that does not perform time synchronization with a distributionserver is enabled to request acquisition of video data at a suitabletiming without the necessity to change the time. To provide such amechanism, for example, the following configuration is included.

According to an aspect of the present invention, a video imagedistribution apparatus includes a reception unit configured to receive avideo data distribution start request from a client apparatus, anextraction unit configured to extract, from the video data distributionstart request, information indicating a client time measured by theclient apparatus as a transmission timing at which the client apparatustransmits the video data distribution start request, in a case where theextraction unit receives the video data distribution start request, afirst determination unit configured to determine a video datadistributable time based at least on the client time, and a transmissionunit configured to transmit the video data distributable time to theclient apparatus.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an entire view illustrating a video image distribution system.

FIG. 2 illustrates a hardware configuration of a camera serverapparatus.

FIG. 3 illustrates a functional configuration of the camera serverapparatus.

FIG. 4 is a sequence diagram illustrating a process of video imagedistribution.

FIG. 5 is a flowchart illustrating a process of video imagedistribution.

FIG. 6 is a flowchart illustrating a process of distributable timedetermination.

FIG. 7 is a relationship diagram illustrating timings of video imagegeneration and distribution request.

FIG. 8 is a flowchart illustrating a process of distributable timedetermination.

DESCRIPTION OF THE EMBODIMENTS

Various exemplary embodiments of the present invention will be describedbelow with reference to the drawings.

FIG. 1 is an entire view illustrating a video image distribution system100 according to a first exemplary embodiment. The video imagedistribution system 100 includes a camera server apparatus 110 and aclient apparatus 120. The camera server apparatus 110 and the clientapparatus 120 are connected with each other via a network 130. Thecamera server apparatus 110 includes a camera and distributes capturedvideo data to the client apparatus 120 via the network 130. The clientapparatus 120 accesses the camera server apparatus 110 to acquire thevideo data. The camera server apparatus 110 may also be referred to as avideo image distribution apparatus, as it is configured to control thedistribution of video images in a video image distribution system aswill be described below.

While FIG. 1 illustrates only one camera server apparatus 110 tosimplify the description, the video image distribution system 100 caninclude two or more camera server apparatuses 110. Further, there can bea client apparatus, which accesses the camera server apparatus 110 toreceive an image, other than the client apparatus 120. The network 130includes a plurality of routers, switches, and cables that satisfiescommunication standards such as Ethernet®. The communication standards,scale, and configuration of the network 130 are not particularlylimited. The network 130 can be, for example, from the Internet to alocal area network (LAN).

While video data is described as distribution target data of the cameraserver apparatus 110 in the present exemplary embodiment, thedistribution target data can include data other than video data.Examples of data other than video data include audio data, image/audioanalysis data, and caption data.

FIG. 2 illustrates a hardware configuration of the camera serverapparatus 110. A central processing unit (CPU) 200, a primary storageapparatus 201, a secondary storage apparatus 202, an image captureinterface (I/F) 203, and a network I/F 204 are connected with oneanother via an internal bus 206. The CPU 200 controls the entire cameraserver apparatus 110. The primary storage apparatus 201 is a high-speedwritable storage apparatus such as a random-access memory (RAM), and anoperating system (OS), various programs, and various types of data areloaded into the primary storage apparatus 201. Further, the primarystorage apparatus 201 is also used as a work area of the OS and thevarious programs. The secondary storage apparatus 202 is a non-volatilestorage apparatus such as a flash memory, hard disk drive (HDD), orsecure digital (SD) card and is used as a permanent storage area for theOS, the various programs, and various types of data as well as atemporary storage area for various types of data. The CPU 200 reads andexecutes a program stored in the secondary storage apparatus 202 torealize the functions and processing of the camera server apparatus 110described below.

The image capture OF 203 is connected with a sensor (image sensor) 205consists of a charge-coupled device (CCD) sensor or a complementarymetal oxide semiconductor (CMOS) sensor. The image capture OF 203converts image data acquired from the sensor 205 into a predeterminedformat, compresses the converted image data, and transfers thecompressed image data to the primary storage apparatus 201. The networkOF 204 is an interface for connecting to the network 130 and performscommunication with the client apparatus 120, etc.

FIG. 3 illustrates a functional configuration of the camera serverapparatus 110. An image capturing processing unit 301 acquires a videoframe generated by the sensor 205 via the image capture OF 203, performsencoding processing on the acquired video frame, and stores the encodedvideo frame in the primary storage apparatus 201. The primary storageapparatus 201 temporarily stores the generated video frame. The videoframe stored in the primary storage apparatus 201 is erased after thedistribution of the video frame is completed.

When a distribution management unit 302 receives a distribution startrequest from the client apparatus 120, the distribution management unit302 transmits a media presentation description (MPD) file including adistributable time and distributable video image stream information tothe client apparatus 120 via a network processing unit 303. Thedistribution start request is a MPD file acquisition request. Thedistribution management unit 302 further converts a single or aplurality of video frames accumulated in the primary storage apparatus201 into a transmittable segment file (moving image file). Then, thedistribution management unit 302 transmits the segment file to theclient apparatus 120 via the network processing unit 303 according tothe request from the client apparatus 120.

Alternatively, in the cases in which a protocol such as HypertextTransfer Protocol (HTTP)/2 or WebSocket is employed, the distributionmanagement unit 302 can transmit segment files one after another eachtime a video frame is generated, and a segment file is completelygenerated without receiving a request. While the distribution managementunit 302 converts the video frames into the segment files in the abovedescription, a common segment file for all clients can be generated atthe time of video image generation.

FIG. 4 is a sequence diagram illustrating a process of video imagedistribution from the camera server apparatus 110 to the clientapparatus 120. In step S401, the client apparatus 120 transmits, to thecamera server apparatus 110, a distribution start request including atime (T1) measured by the client apparatus 120 at the time point of theprocessing in step S401 (transmission time point). Hereinafter, the time(T1) measured by the client apparatus 120 will be referred to as a“client time”. If the camera server apparatus 110 receives thedistribution start request, then in step S402, the camera serverapparatus 110 starts video image generation to generate a distributablevideo image stream. In step S403, the camera server apparatus 110determines, as a distributable time (T2), a value obtained by adding areference time (D1) for distributable video data to be prepared to theclient time (T1) included in the distribution start request. Details ofthe reference time (D1) will be described below.

In step S404, the camera server apparatus 110 generates a MPD file towhich the distributable time (T2) is set as an availability start time,and transmits the generated MPD file to the client apparatus 120. Instep S405, the camera server apparatus 110 generates a video frame 1(I-frame) including a sequence parameter set and a picture parameter set(SPS/PPS), etc. In step S406, the camera server apparatus 110 generatesan initialization segment that is a first video data from the SPS/PPS,etc. In step S407, the camera server apparatus 110 generates a videoframe 2 (P-frame) that is a difference video image from the video frame1. In step S408, the camera server apparatus 110 generates a video frame3 (P-frame) that is a difference video image from the video frame 2. Instep S409, the camera server apparatus 110 generates a medium segment 1from the video frames 1, 2, and 3. While the difference video images areP-frames in the present exemplary embodiment, the difference videoimages can be B-frames.

Subsequently, when the current time of the processing time point becomesthe time set as the availability start time of the MPD file, then instep S410, the client apparatus 120 transmits an initialization segmentacquisition request to the camera server apparatus 110. In step S411,the client apparatus 120 receives the initialization segment as aresponse from the camera server apparatus 110. In step S412, the clientapparatus 120 transmits a request for acquisition of the medium segment1 to the camera server apparatus 110. In step S413, the client apparatus120 receives the medium segment 1 as a response from the camera serverapparatus 110. While the client apparatus 120 acquires theinitialization segment at or after the distributable time in the presentexemplary embodiment, the client apparatus 120 can acquire theinitialization segment before the distributable time, since theinitialization segment can be generated in advance.

Similarly, in step S414, the camera server apparatus 110 generates avideo frame 4 (I-frame). In step S415, the camera server apparatus 110generates a video frame 5 (P-frame). In step S416, the camera serverapparatus 110 generates a video frame 6 (P-frame). In step S417, thecamera server apparatus 110 generates a medium segment 2 from the videoframes 4, 5, and 6. Then, in step S418, the client apparatus 120transmits a request for acquisition of the medium segment 2 to thecamera server apparatus 110 at or after the time at which the mediumsegment 2 is generated. In step S419, the client apparatus 120 receivesthe medium segment 2 as a response from the camera server apparatus 110.

FIG. 5 is a flowchart illustrating a process of video image distributionby the camera server apparatus 110. The process of video imagedistribution is executed at the time of reception of the distributionstart request from the client apparatus 120. In step S501, thedistribution management unit 302 transmits, to the image capturingprocessing unit 301, an instruction to start video image generation togenerate a distributable video image stream. In step S502, thedistribution management unit 302 determines the distributable time basedon the client time (T1) included in the distribution start request. Theprocessing in step S502 will be described below with reference to FIG.6.

In step S503, the distribution management unit 302 sets thedistributable time determined in step S502 as the availability starttime of the MPD file, and generates the MPD file. In step S504, thedistribution management unit 302 transmits the MPD file to the clientapparatus 120 via the network processing unit 303. In step S505, thedistribution management unit 302 waits until an event occurs, and in acase where an event occurs (YES in step S505), the processing proceedsto step S506.

In step S506, the distribution management unit 302 determines a type ofthe event. In a case where the distribution management unit 302determines that a type of the event is a video frame generation event(“video frame generation event” in step S506), the processing proceedsto step S507. In a case where the distribution management unit 302determines that a type of the event is a segment acquisition requestevent (“segment acquisition request event” in step S506), the processingproceeds to step S510. The segment acquisition request is informationthat requests acquisition of the initialization segment or mediumsegment. In a case where the distribution management unit 302 determinesthat a type of the event is a distribution end event (“distribution endevent” in step S506), the processing proceeds to step S515.

In step S507, the distribution management unit 302 buffers the videoframe in the primary storage apparatus 201. At this time, thedistribution management unit 302 stores not only the video frame butalso information such as SPS/PPS in a buffer. In step S508, thedistribution management unit 302 determines whether the buffer is full.In a case where the distribution management unit 302 determines that thebuffer is not full (NO in step S508), the processing proceeds to stepS505. On the other hand, in a case where the distribution managementunit 302 determines that the buffer is full (YES in step S508), theprocessing proceeds to step S509. In step S509, the distributionmanagement unit 302 releases an old video frame, and then the processingproceeds to step S505.

In step S510, the distribution management unit 302 determines whetherthe requested information included in the requested segment is stored inthe buffer. In a case where the distribution management unit 302determines that the requested information is stored in the buffer (YESin step S510), the processing proceeds to step S511. On the other hand,in a case where the distribution management unit 302 determines that therequested information is not stored in the buffer (NO in step S510), theprocessing proceeds to step S514. In step S511, the distributionmanagement unit 302 generates the requested segment (initializationsegment or medium segment). The distribution management unit 302 can setthe time of the initialization segment or one of the medium segmentsfrom the distributable time as a start point, as the time to be includedin the initialization segment or medium segment to be generated. In stepS512, the distribution management unit 302 transmits the segmentgenerated in step S511 to the client apparatus 120. In step S513, thedistribution management unit 302 releases the transmitted video framefrom the buffer, and then the processing proceeds to step S505.

In step S514, the distribution management unit 302 transmits an errorresponse to the client apparatus 120, and then the processing proceedsto step S505. In step S515, the distribution management unit 302releases all the information stored in the buffer. In step S516, thedistribution management unit 302 transmits an instruction to stop thevideo image generation to the image capturing processing unit 301. Then,the process of video image distribution ends.

FIG. 6 is a flowchart illustrating details of distributable timedetermination processing (step S502) described above with reference toFIG. 5. As a premise, there is a case in which the client time isincluded in the MPD file received by the camera server apparatus 110from the client apparatus 120 and a case in which the client time is notincluded in the received MPD file. Similarly, there is a case in which asegment time is included in the MPD file received by the camera serverapparatus 110 from the client apparatus 120 and a case in which thesegment time is not included in the received MPD file. As used herein,the segment time is a time that is set by a user of the client apparatus120 as the time needed for the camera server apparatus 110 to prepare adistributable segment.

In step S601, the distribution management unit 302 determines whetherthe client time (T1) is designated in the MPD file. In a case where thedistribution management unit 302 determines that the client time (T1) isdesignated (YES in step S601), the processing proceeds to step S602. Ina case where the distribution management unit 302 determines that theclient time (T1) is not designated (NO in step S601), the processingproceeds to step S603. In step S602, the distribution management unit302 extracts the client time (T1) from the MPD file and sets the clienttime (T1) as the start time (T2), and then the processing proceeds tostep S604. On the other hand, in step S603, the distribution managementunit 302 sets, as the start time (T2), the current time (server time)measured by the camera server apparatus 110 at the time point of theprocessing in step S603, and then the processing proceeds to step S604.As used herein, the client time (T1) is a time that is measured by theclient apparatus 120 as a transmission timing at which the clientapparatus 120 transmits the distribution start request. Further, theserver time is a time that is measured by the camera server apparatus110 as a reception timing at which the camera server apparatus 110receives the distribution start request.

In step S604, the distribution management unit 302 determines whetherthe segment time is designated in the MPD file. In a case where thedistribution management unit 302 determines that the segment time isdesignated (YES in step S604), the processing proceeds to step S605. Ina case where the distribution management unit 302 determines that thesegment time is not designated (NO in step S604), the processingproceeds to step S606. In step S605, the distribution management unit302 sets the segment time as the reference time (D1), and then theprocessing proceeds to step S607. On the other hand, in step S606, thedistribution management unit 302 sets, as the reference time (D1), agroup-of-pictures (GOP) time interval, which is a time interval from anI-frame to an I-frame. For example, the GOP time interval is a periodthat corresponds to a time period for generating three video frames. TheGOP time interval is set as a default value of the reference time (D1)in the camera server apparatus 110. The default value can be a valuethat is preset in the camera server apparatus 110 and is not limited tothe GOP time interval. Further, the time set as the default value can bedifferent for each video image stream. In step S607, the distributionmanagement unit 302 determines, as the distributable time, a valueobtained by adding the reference time (D1) to the start time (T2). Then,the distributable time determination processing (step S502 in FIG. 5)ends.

As described above, in the video image distribution system 100 in thefirst exemplary embodiment, the camera server apparatus 110 receives thecurrent time from the client apparatus 120 to determine the distributionstart time at the client apparatus 120 and transmits the determineddistribution start time to the client apparatus 120. This enables theclient apparatus 120 to transmit a segment acquisition request to thecamera server apparatus 110 at a suitable timing without the necessityto change the time. In this way, a mechanism is provided by which aclient apparatus that does not perform time synchronization with adistribution server is enabled to request acquisition of video data at asuitable timing without the necessity to change the time.

In a first modified example of the first exemplary embodiment, in stepS607, the distribution management unit 302 is only required to determinethe distributable time based on the start time (T2) and the referencetime (D1), and a specific process for the determination is not limitedto the process described in the present exemplary embodiment. In anotherexample, the distribution management unit 302 can add a value obtainedby multiplying the reference time (D1) by 1.5 or 0.5 to the start time(T2).

In a second modified example, the reference time can be set to zeroseconds if the segment time is short enough to be ignored, e.g., if thesegment time is less than one second. Specifically, the client time candirectly be determined as the video data distributable time.

In a third modified example, in step S607, the distribution managementunit 302 can further determine the distributable time by adding timeother than the reference time (D1) needed to enable distribution to theclient apparatus 120. For example, the distribution management unit 302can add a round trip time (RTT) needed for the communication between thecamera server apparatus 110 and the client apparatus 120.

In a fourth modified example, the distributable time can be used as timeinformation other than the availability start time. For example, thedistributable time can be used as a publish time for use in an in-bandevent stream, etc.

Now, the following describes the video image distribution system 100according to a second exemplary embodiment, focusing on differencescompared to the video image distribution system 100 according to thefirst exemplary embodiment described above. FIG. 7 is a relationshipdiagram illustrating the timings of video image generation anddistribution request in the second exemplary embodiment. In FIG. 7, thehorizontal axis of the graph represents the number of a generated videoframe, and the vertical axis of the graph represents time. Further, astraight line 700 indicates the time with respect to the number of agenerated frame. As illustrated in FIG. 7, a segment 1 is generated atthe timing (T11) at which a frame of the frame number 3 is generated.Further, a segment 2 is generated at the timing (T12) at which a frameof the frame number 6 is generated. Furthermore, the camera serverapparatus 110 receives a distribution start request from the clientapparatus 120 at a timing (T20) between the timings T11 and T12.

In this case, the camera server apparatus 110 is to start furtherdistribution starting with the segment 1 that has been previouslygenerated. The camera server apparatus 110 calculates the differencetime (D2) between the timing (T20) and the time (T11) at which thesegment 1 is generated. The difference time (D2) is obtained from“T20−T11”. In this case, the start time (T2) is obtained from “T1−D2”.Further, there can be a case in which the camera server apparatus 110 isto start distribution starting with the segment 2 that is to begenerated next by the camera server apparatus 110. In this case, thecamera server apparatus 110 calculates the difference time (D3) betweenthe time (T12) at which the segment 2 is generated and the timing (T20).The difference time (D3) is obtained from “T12−T20”. In this case, thestart time (T2) is obtained from “T1+D3”.

FIG. 8 is a flowchart illustrating a process of distributable timedetermination in the second exemplary embodiment. Steps S801 to S803 aresimilar to steps S601 to S603 described above with reference to FIG. 6.Then, in step S804, the distribution management unit 302 determineswhether a distributable segment is stored in the buffer as a temporarystorage unit 304. In a case where the distribution management unit 302determines that a distributable segment is stored (YES in step S804),the processing proceeds to step S805. In a case where the distributionmanagement unit 302 determines that no distributable segment is stored(NO in step S804), the processing proceeds to step S807.

In step S805, the distribution management unit 302 calculates thedifference time (D2). In step S806, the distribution management unit 302determines, as the distributable time, a value obtained by subtractingthe difference time (D2) from the start time (T1). Then, the process ofdistributable time determination ends. On the other hand, in step S807,the distribution management unit 302 calculates the difference time(D3). In step S808, the distribution management unit 302 determines, asthe distributable time, a value obtained by adding the difference time(D3) to the start time (T1). Then, the process of distributable timedetermination ends.

As described above, if there is a distributable segment in the buffer,the camera server apparatus 110 in the second exemplary embodimentstarts distribution starting with the segment stored in the buffer. Onthe other hand, if no distributable segment is in the buffer, the cameraserver apparatus 110 starts distribution starting with a segment to begenerated. The configuration and processing of the video imagedistribution system 100 in the second exemplary embodiment other thanthose described above are similar to those of the video imagedistribution system 100 in the first exemplary embodiment.

In a modified example of the second exemplary embodiment, thedistribution management unit 302 can start distribution starting with asegment to be generated next even in the case in which a distributablesegment is stored in the buffer. The distribution management unit 302can start distribution starting with a segment to be generated next if,for example, an instruction is provided from the client apparatus 120.

While a Moving Picture Experts Group-Dynamic Adaptive Streaming overHypertext Transfer Protocol (MPEG-DASH) distribution method is describedas an example in the above-described exemplary embodiments, the presentinvention is also applicable to a distribution method using differentHTTP adaptive streaming, such as HTTP Live Streaming (HLS), and adistribution method using any other time information.

While the exemplary embodiments of the present invention have beendescribed in detail, the present invention is not to be limited by anyspecific exemplary embodiment of the present invention, and variousmodifications and changes are possible within the spirit of the claimedinvention.

The above-described exemplary embodiments each provide a mechanism bywhich a client apparatus that does not perform time synchronization witha distribution server is enabled to request acquisition of video data ata suitable timing without the necessity to change the time.

OTHER EMBODIMENTS

Embodiment(s) of the present invention can also be realized by acomputer of a system or apparatus that reads out and executes computerexecutable instructions (e.g., one or more programs) recorded on astorage medium (which may also be referred to more fully as a‘non-transitory computer-readable storage medium’) to perform thefunctions of one or more of the above-described embodiment(s) and/orthat includes one or more circuits (e.g., application specificintegrated circuit (ASIC)) for performing the functions of one or moreof the above-described embodiment(s), and by a method performed by thecomputer of the system or apparatus by, for example, reading out andexecuting the computer executable instructions from the storage mediumto perform the functions of one or more of the above-describedembodiment(s) and/or controlling the one or more circuits to perform thefunctions of one or more of the above-described embodiment(s). Thecomputer may comprise one or more processors (e.g., central processingunit (CPU), micro processing unit (MPU)) and may include a network ofseparate computers or separate processors to read out and execute thecomputer executable instructions. The computer executable instructionsmay be provided to the computer, for example, from a network or thestorage medium. The storage medium may include, for example, one or moreof a hard disk, a random-access memory (RAM), a read only memory (ROM),a storage of distributed computing systems, an optical disk (such as acompact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™),a flash memory device, a memory card, and the like.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2017-235238, filed Dec. 7, 2017, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. A video image distribution apparatus comprising:a reception unit configured to receive a video data distribution startrequest from a client apparatus; an extraction unit configured toextract, from the video data distribution start request, informationindicating a client time measured by the client apparatus as atransmission timing at which the client apparatus transmits the videodata distribution start request, in a case where the extraction unitreceives the video data distribution start request; a firstdetermination unit configured to determine a video data distributabletime based at least on the client time; and a transmission unitconfigured to transmit the video data distributable time to the clientapparatus.
 2. The video image distribution apparatus according to claim1, wherein the first determination unit determines the video datadistributable time based on the client time and a reference time for thevideo data distribution.
 3. The video image distribution apparatusaccording to claim 2, wherein the first determination unit determines,as the video data distributable time, a time obtained by adding thereference time to the client time.
 4. The video image distributionapparatus according to claim 3, wherein, in a case where distributablevideo data is not stored in a temporary storage unit, the firstdetermination unit determines, as the video data distributable time, atime obtained by adding the reference time to the client time.
 5. Thevideo image distribution apparatus according to claim 2, wherein, in acase where distributable video data is stored in a temporary storageunit, the first determination unit determines, as the video datadistributable time, a time obtained by subtracting the reference timefrom the client time.
 6. The video image distribution apparatusaccording to claim 2, wherein the reference time is a time that ispreset to the video image distribution apparatus.
 7. The video imagedistribution apparatus according to claim 2, wherein the reception unitfurther receives designation of the reference time from the clientapparatus, and wherein the first determination unit determines the videodata distributable time based on the reference time received from theclient apparatus.
 8. The video image distribution apparatus according toclaim 7, wherein, in a case where the designation of the reference timeis received from the client apparatus, the first determination unitdetermines the video data distributable time based on the reference timedesignated by the client apparatus, and, in a case where the designationof the reference time is not received from the client apparatus, thefirst determination unit determines the video data distributable timebased on the reference time that is preset to the video imagedistribution apparatus.
 9. The video image distribution apparatusaccording to claim 2, wherein, in a case where the video datadistribution start request does not include the client time, the firstdetermination unit determines the video data distributable time based onthe reference time and a time measured by the video image distributionapparatus as a reception timing at which the reception unit receives thevideo data distribution start request.
 10. A control method that isexecuted by a video image distribution apparatus, the method comprising:receiving a video data distribution start request from a clientapparatus; extracting, from the video data distribution start request,information indicating a client time measured by the client apparatus asa transmission timing at which the client apparatus transmits the videodata distribution start request, in a case where the video datadistribution start request is received; determining a video datadistributable time based at lease on the client time; and transmittingthe video data distributable time to the client apparatus.
 11. Anon-transitory computer-readable recording medium that stores a programfor causing a computer to function as: a reception unit configured toreceive a video data distribution start request from a client apparatus;an extraction unit configured to extract, from the video datadistribution start request, information indicating a client timemeasured by the client apparatus as a transmission timing at which theclient apparatus transmits the video data distribution start request, ina case where the extraction unit receives the video data distributionstart request; a first determination unit configured to determine avideo data distributable time based at least on the client time; and atransmission unit configured to transmit the video data distributabletime to the client apparatus.